Dendritic Cells in the Breaking of Peripheral Tolerance in Type 1 Diabetes

描述（由申请人提供）：1型糖尿病（T1D）是最常见的儿童自身免疫性疾病，是由T淋巴细胞介导的胰岛素生成胰腺β细胞破坏引起的。T1D的显著免疫学特征在非肥胖糖尿病（NOD）小鼠中得到了很好的模拟，与人类T1D患者一样，它们表现出由CD4+和CD8+ T细胞介导的自发性自身免疫性糖尿病。虽然这些致糖尿病或致病的T细胞是不可或缺的细胞参与者，但它们的激活和功能成熟是由先天抗原呈递细胞（APC）控制的，APC以一种破坏正常外周T细胞耐受性的方式获取、加工和呈递胰腺β细胞抗原。负责破坏T细胞耐受性的APC及其分子机制尚不清楚。树突状细胞（DC）在炎症期间将外来抗原呈递给T细胞是至关重要的。然而，DC对凋亡自身细胞的清除通常被认为是非炎症性的，甚至是耐受性的；事实上，大量研究表明，从凋亡细胞中捕获抗原的DC迁移到局部淋巴结，在那里它们诱导T细胞耐受、能量或缺失。然而，在某些情况下，DC对凋亡细胞的吞噬可能是促炎的，并导致启动自反应性T细胞；这被认为是在t1d易感个体或动物中出现胰腺细胞凋亡的情况。最近，我们发现常规DC （cDC）的一个子集对于在体内启动糖尿病性CD4+ T细胞是必需的。有趣的是，在这个cDC人群中，我们的同事和双pi申请人Edith Janssen博士描述了一种新的DC亚群（CD11c+CD11blo/-CD4- cd81 - pdca -1-），与其他cDC亚群相比，它有效地（交叉）将CD4+和CD8+ T细胞从凋亡细胞中导入自身抗原。这些细胞被称为merocytic DC (mcDC)，因为它们将凋亡细胞的颗粒储存在细胞质中的离散点状囊泡中，meros (<5A？C，粒子，在希腊语中)。例如，CD8+ T细胞遇到暴露于凋亡抗原的mcDC时，并不表现出耐受性，而是表现出增强的原克隆扩增、细胞因子产生和效应功能。此外，mcDC通过产生大量的1型干扰素来增强对凋亡自我的炎症免疫。理由：我们最近的研究发现，与其他菌株相比，NOD小鼠中的mcDC不仅数量更多，而且生物活性更高。装载胰岛抗原的mcDC (i)拯救CD8+ T细胞免受外周能量和缺失，（ii）刺激胰岛反应性CD4+ T细胞，（iii）将糖尿病转移给年轻的NOD受体。此外，从明显糖尿病NOD小鼠的胰腺淋巴结中纯化后，mcDC可以在体内破坏外周T细胞对β细胞抗原的耐受性，并在年轻NOD小鼠中诱导快速发作的T细胞介导的T1D。因此，mcDC亚群似乎代表了长期寻找的关键抗原提呈细胞，负责打破体内外周对β细胞抗原的耐受性。假设：总之，这些结果使我们假设mcDC是(i)关键的CD11c+ DC亚群，负责启动糖尿病性T细胞并导致对胰岛抗原免疫耐受的功能中断，以及（ii） NOD小鼠中驱动T1D所需的1型干扰素的主要储存库。为了对这些假设进行直接检验，我们提出以下具体目标：目的1：确定胰岛抗原供血mcDC在NOD小鼠中破坏CD4+和CD8+ T细胞耐受性的方法。初步数据表明，从凋亡的β细胞获得和呈递自身抗原可破坏体内外周CD4+和CD8+ T细胞的耐受性。目的2：明确mcDC产生1型干扰素在NOD小鼠T1D发展中的分子作用。

DESCRIPTION (provided by applicant): Type 1 diabetes (T1D), the most common childhood autoimmune disease, is caused by the T lymphocyte-mediated destruction of insulin-producing pancreatic beta cells. The salient immunological features of T1D are well-modeled in the non-obese diabetic (NOD) mouse, which like human T1D patients exhibit spontaneous autoimmune diabetes mediated by both CD4+ and CD8+ T cells. While these diabetogenic, or disease-causing, T cells are indispensable cellular participants, their activation and functional maturation are controlled by the innate antigen presenting cells (APC) which acquire, process and present pancreatic beta cell antigen in a manner that breaks normal peripheral T cell tolerance. The APC responsible for breaking T cell tolerance and the molecular mechanism involved is not well understood. It is well appreciated that dendritic cells (DC) are crucial for presenting foreign antigen to T cells during times of inflammation. Yet, the clearance of apoptotic self cells by DC is generally considered to be non-inflammatory, even tolerogenic; in fact, numerous studies have shown that DC that capture antigen from apoptotic cells migrate to local lymph nodes, where they induce T cell tolerance, anergy or deletion. Yet, under certain situations phagocytosis of apoptotic cells by DC can be pro-inflammatory and lead to the priming of self-reactive T cells; this is thought to be the case for the presentation of apoptotic pancreatic beta cells in T1D-prone individuals or animals. Recently, we found that a subset of conventional DC (cDC) are necessary for priming diabetogenic CD4+ T cells in vivo. Interestingly, within this cDC population, our colleague and dual-PI applicant, Dr. Edith Janssen, described a novel DC subset (CD11c+CD11blo/-CD4-CD81-PDCA-1-) that in contrast to other cDC subsets potently (cross-)primes both CD4+ and CD8+ T cells to self-antigen from apoptotic cells. These cells are termed merocytic DC (mcDC) since they stored particles of apoptotic cells in discrete, punctate vesicles in their cytoplasm, meros (<5A?C, particle, in Greek). For example, CD8+ T cells that encounter mcDC exposed to apoptotic antigen are not rendered tolerant, but rather display enhanced primary clonal expansion, cytokine production and effector function. Moreover, mcDC enhance inflammatory immunity to apoptotic self in part by producing copious levels of type 1 interferons. Rationale: Our recent studies have found that mcDC are not only more numerous but also more biologically active in NOD mice compared to other strains. Islet antigen-loaded mcDC (i) rescue CD8+ T cells from peripheral anergy and deletion, (ii) stimulate islet-reactive CD4+ T cells, and (iii) transfer diabetes to young NOD recipients. Moreover, when purified from the pancreatic lymph nodes of overtly diabetic NOD mice, mcDC can break peripheral T cell tolerance to beta cell antigens in vivo and induce rapid onset T cell-mediated T1D in young NOD mouse. Thus, the mcDC subset appears to represent the long-sought critical antigen presenting cell responsible for breaking peripheral tolerance to beta cell antigen in vivo. Hypothesis: Together, these results lead us to hypothesize that mcDC are (i) the critical CD11c+ DC subset responsible for the priming of diabetogenic T cells and cause the functional break in immune tolerance to islet antigen, and (ii) a major reservoir of type 1 interferon needed to drive T1D in NOD mice. To provide a direct test of these hypotheses, we propose the following specific aims: Aim 1: To identify the means by which islet-antigen-fed mcDC break CD4+ and CD8+ T cell tolerance in the NOD mouse. Preliminary data shows that the acquisition and presentation of self-antigen from apoptotic beta cells breaks peripheral CD4+ and CD8+ T cell tolerance in vivo. Aim 2: To define the molecular role of type 1 interferon production by mcDC in the development of T1D in the NOD mouse. PUBLIC HEALTH RELEVANCE: This application focuses on Type 1 diabetes (T1D), the most common childhood autoimmune disease, is caused by the T lymphocyte-mediated destruction of insulin-producing pancreatic beta cells. The salient immunological features of T1D are well-modeled in the non-obese diabetic (NOD) mouse, which like human T1D patients exhibit spontaneous autoimmune diabetes mediated by both CD4+ and CD8+ T cells. While these diabetogenic, or disease-causing, T cells are indispensable cellular participants, their activation and functional maturation are controlled by the innate antigen presenting cells (APC) which acquire, process and present pancreatic beta cell antigen in a manner that breaks normal peripheral T cell tolerance. The APC responsible for breaking T cell tolerance and the molecular mechanism involved is not well understood. Recently, we found that a subset of conventional DC (cDC) are necessary for priming diabetogenic CD4+ T cells in vivo. Interestingly, within this cDC population, our colleague and dual-PI applicant, Dr. Edith Janssen, described a novel DC subset termed merocytic DC (mcDC) which store particles of apoptotic cells in discrete, punctate vesicles in their cytoplasm. Additionally, mcDC enhance inflammatory immunity to self tissue in part by producing copious levels of type 1 interferons. Our recent studies have found that mcDC are not only more numerous but also more biologically active in NOD mice compared to other strains. We hypothesize that mcDC are (i) the critical CD11c+ DC subset responsible for the priming of diabetogenic T cells and cause the functional break in immune tolerance to islet antigen, and (ii) a major reservoir of type 1 interferon needed to drive T1D in NOD mice.